Mechanics and Mechanical Engineering 2019; 23:59–63

Research Article

S. Dharani Kumar* and S. Sendhil Kumar

Investigation of mechanical behavior of friction

stir welded joints of AA6063 with AA5083
aluminum alloys
https://doi.org/10.2478/mme-2019-0008 dealt with, but the efficiency of the joint is unsatisfactory. A
Received Apr 3, 2018; revised Jun 5, 2018; accepted Nov 20, 2018 suitable filler material is a crucial problem in fusion weld-
ing process. Friction stir welding (FSW), developed by the
Abstract: Aluminum alloy finds its applications in various
Welding Institute (TWI) in 1991 [1], is the available option
sectors of engineering. This paper discusses the investiga-
to overcome the above mentioned problems. It is a solid
tion of mechanical characteristics of butt weld joints of alu-
state welding process, which has many advantages such
minum alloy AA6063 along with AA5083. An experiment
as joining of dissimilar aluminum alloys, possessing ex-
was conducted for different tool rotational speeds of 600
cellent mechanical properties when compared to TIG and
rpm, 800 rpm and 1000 rpm. Specifications of friction stir
MIG welding [2], grain refinement with fine distribution
welding machine were 4 kN axial load and welding speed
of precipitates (which is an evidence of better strength)
of 40 mm/min. Friction stir welded (FSW) joints of higher
and ductility [3]. The results indicate that 79% joint effi-
tensile strength, lower flexural strength and lower impact
ciency is achieved with tensile strength of 289 MPa for
strength with maximum hardness, for the work piece fab-
FSW joints, whereas the best tensile strength of 210 MPa
ricated at 1000 rpm using a high speed steel tool with a
with 57 % joint efficiency is achieved using TIG welding [4].
cylindrical profile was observed. Better understanding of
A dissimilar FSW process was carried out by placing the
the effect of tool rotational speed and mechanical proper-
high strength aluminum alloy AA204-T6 on the retreating
ties was illustrated through the experimental result.
side and alloy AA5083-H321 on the advancing side [5]. In
Keywords: Aluminum alloy, tensile strength, impact AA7075-AA2024 dissimilar welds, the tensile properties in
strength, cylindrical pin profile the longitudinal direction of the stirred zone were found to
be better when the AA7075 alloy is placed on the advanc-
ing side [6]. The welds that are fabricated using straight
tool profiles have no defects, while the tapered tool profiles
1 Introduction
cause tunnel at the bottom of joints [7]. Structurally, trans-
formation occurs in dissimilar friction stir weld of AA5083-
Aluminum alloy finds its application in aeronautical, au-
O and AA6082-T6 aluminum alloys when the weld is an-
tomobile and marine industries with different configura-
odized in H2 SO4 solution [8]. Effects of the sleeve plunging
tions. Welding of dissimilar aluminum alloy with thick-
speed on the microstructure and lap shear failure load of
ness more than 3 mm is quite difficult in the fusion weld-
the dissimilar 6063/5083 joints were discussed [9]. In the
ing processes. The major defect noted in dissimilar fusion
FSW process, two different grade aluminum alloys can be
welding is of solidification cracks in the heat affected zone.
used with AA6063 as the heat treatable alloy and AA5083
Welding porosity occurs during fusion as a result of vary-
as the non-heat treatable alloy. Hence, the combinations
ing degree and speed of the welding processes. Joining of
of these alloys are used in ship hulls and automobile inner
dissimilar aluminum alloy materials with different prop-
panels. Hence, preliminary investigation was carried out
erties using conventional fusion welding process can be
in this area of research to understand the mechanical prop-
erties like tensile, bending, impact, toughness and hard-
ness of dissimilar FSW joints over tool rotational speeds.
*Corresponding Author: S. Dharani Kumar: Department of Me- This paper discusses the relation between the mechanical
chanical Engineering, Sri Eshwar College of Engineering, Coimbat-
properties and tool rotational speed of friction stir welded
ore - 641202, India; Email: sdharanikumarmech@gmail.com
S. Sendhil Kumar: Department of Mechanical Engineering, AA5083 with AA6063 aluminum alloy joints. The follow-
Info Institute of Engineering, Coimbatore - 641107, India; Email: ing sections discuss the experimental work, results and
ssk333c@yahoo.co.in

Open Access. © 2019 et al., published by Sciendo. This work is licensed under the Creative Commons Attribution-NonCommercial-
NoDerivatives 4.0 License
60 | S. Dharani Kumar and

discussions of the FSW carried out using two different alu- Table 1: Chemical composition of the material AA6063 and AA5083
minum alloys, namely AA 6063 and AA5083.
Alloying 6063 5083
Elements
Al Bal Bal
2 Experimental work Si 0.20–0.60 0.7–1.3
Fe 0.0–0.35 0.50 max
Chemical composition and mechanical properties for alu- Cu 0.0–0.10 0.10 max
minum alloy are tabulated in Table 1 and Table 2 respec- Mn 0.0–0.10 0.40–1.00
tively. The rolled plates with 6 mm thickness of AA6063 Cr 0.0–0.10 0.25 max
aluminum alloy and AA5083 aluminum alloy have been Mg 0.45-0.49 0.06–1.20
slashed into the required size of 100 mm × 50 mm × 6 Zn 0.0–0.10 0.20 max
mm and grinded to achieve a superior surface finish. The Ti 0.0–0.10 0.10 max
square butt joint configuration is selected for FSW weld- Other Each 0–0.05 0.05 max
ing. There are two inverting positions in FSW welding for Others Total 0–0.15 0.15 max
the base metal AA6063 placed in retreating side (RS), while
AA5083 is placed in the advanced side (AS). The aluminum
alloy of AA6063 is placed in the retreating side due to
its lower tensile strength. A non-consumable rotating tool
made of high speed steel (HSS) is shown in Figure 1(a). The
tool pin is a straight cylindrical profile with shoulder di-
ameter of 20 mm, 5 mm pin diameter, 5 mm pin tip length
and D/d ratio of 4. The friction stir welds using AA5083 and
AA6063 aluminum alloys were fabricated using a FSW ma-
chine with the motor specifications of 2.2 kW/440V and a
maximum tool rotational speed of 3000 rpm. The welds Figure 2: Friction stir Welded specimens of different tool rotational
speeds
were made along the longitudinal direction of the plate
with the tool rotational speeds of 600, 800 and 1000 rpm,
Table 2: Mechanical properties of base materials
keeping the constant welding speed of 40 mm/min and ax-
ial load of 4 KN.
Base Ultimate tensile Hardness Tensile
metal strength [MPa] Brinell elongation
[HB] [%]
AA6063 130 25 18
AA5083 345 75 12

2.1 Mechanical properties

The mechanical properties of joints like tensile, bending,

impact and hardness are determined. To determine the me-
chanical properties of dissimilar FSW welded joints, tests
were performed as per the American Society for Testing of
Materials standards (ASTM). Tensile and bending test were
Figure 1: (a) Cylindrical tool, (b) Friction Stir welding machine conducted at room temperature using an electromechani-
cal controlled universal testing machine with an ultimate
load of 100 KN. Tensile specimens were prepared as per the
Quality welds can be produced with tool rotation ASTM E8 M04 standard for evaluating the yield strength,
speeds ranging from 600 to 1200 rpm. The single pass ultimate strength and the percentage of elongation of the
welding procedure was adopted for fabrication of dissim- weld joints. The samples were machined along the trans-
ilar joints, which is shown in the Figure 2. verse welding direction. The specimen were prepared for
three point bending test as per the ASTM E22-04 standard
 Investigation of mechanical behavior of friction stir welded joints of AA6063 | 61

for evaluating the ductility of the weld metal, HAZ, test rior tensile properties. This is the result of the effect of
of defects particularly lack of side wall fusion (side bead), higher heat input during welding as it results in good duc-
root fusion penetration of welded joints. Hardness test was tility. This shows that an increase in tool rotational speed
carried out according to the ASTM E10 standards using increases the tensile properties of a joint. The overall obser-
a Brinell hardness testing machine with a 10 mm ball in- vation was that the essential nature of use of higher rota-
denter and a 500 kg load. Impact testing was conducted tional speed for providing good heat input, welds thus ob-
at room temperature using a pendulum type impact test- tained displayed good tensile strength. These reveal that
ing machine with a maximum capacity of 300 J. Charpy the ductility of stir zone is lower than base materials.
impact specimens were prepared as per the ASTM E23-04
standards. The Charpy test was carried out with an impact
testing machine for determining the amount of energy ab-
sorbed in fracture, which was recorded. The absorbed en-
ergy is defined as the impact toughness of the material.

3 Results and Discussion

3.1 Tensile test

Yield strength, tensile strength, percentage of elongation

Figure 4: Transverse tensile specimen
of the dissimilar FSW joints have been evaluated for
three different tool rotational speeds. Three specimens are
tested for each rotation speed and the average of the re-
sults is presented in Figure 3. All the joints have lower yield
strength, tensile strength and percentage of elongation
compared to the base material of both aluminum alloys.
All the joints are fractured along the retreating side, which
is shown in Figure 4. This happened due to the smaller
yield strength and minimum hardness value of the base
material AA6063 compared to the advancing side base ma-
terial AA5083.

Figure 5: Bending test specimen

3.2 Bending test

Three point bending tests were carried out for dissimilar

FSW joints .The transverse face and root bending test were
meant for the evaluation of ductility of the FSW joints for
different tool rotational speed. Table 3 illustrates the re-
Figure 3: Effect of tool rotational speed on transverse tensile proper-
duction in flexible strength, as the tool rotational speed
ties
increases.
The FSW joint becomes brittle and embrittled. Brit-
The influence of the welding speed on the tensile prop- tleness arises due to the decrease in FSW joint ductility,
erties of FSW joints is inferred through Figure 4. Among which is due to embrittlement. After performing the bend-
the three tool rotational speeds, 1000 rpm exhibits supe- ing test, visible cracks are identified across the cross sec-
62 | S. Dharani Kumar and

Table 3: Impact and Bending Strength results

Tool rotational Impact Strength Flexural Strength

speed [Rpm] [J/mm2 ] [MPa]
600 0.46 267.628
800 0.45 267.527
1000 0.43 227.403

tion of the joint for tool rotational speed of 1000 rpm, as

shown in Figure 5.

3.3 Impact test

The Charpy impact strength of dissimilar FSW weld joint

was evaluated and presented for three different tool rota-
tional speeds. Impact strength of FSW joint with the notch
was placed at the weld center line. Table 3 illustrates that
an increase in the tool rotational speed causes reduction
in the impact strength of weld joint due to the evolution of
high heat, resulting in coarse grain structure. The impact
strength for the tool rotational speed of 600 rpm is 0.46
J/mm2 , which is 6.5% higher than the 1000 rpm welded
specimen. All the impact tested specimen do not break into Figure 6: Impact test specimen
two pieces, as shown in the Figure 6, reveals that the FSW
joint does not lose its ductility.

3.4 Hardness test

AA5083-AA6063 for three different tool rotational speeds

is illustrated in Figure 7. The fusion zone has a lower
hardness compared to the base material AA5083 and 68%
higher than the base material value of AA6063. Retreating
side was identified with hardness value of 35 HB and ad-
vancing side hardness value of 75 HB due to the base ma-
terial in the retreating side. The hardness value of the stir Figure 7: Hardness variation from stir zone
zone increases as the tool rotational speed increases. This
was due to the HAZ region by retreating side, that is, 34.07
speeds ranging from 500 rpm to 1200 rpm; with step varia-
HB, which is 36% higher in the base material of AA6063 re-
tion of 200 rpm the axial load and welding speed is main-
vealing the effect of the tool rotational speed on the hard-
tained constant. Investigation of the mechanical proper-
ness of the FSW dissimilar joint. As the rotational speed
ties of fabricated joint and its effects are discussed in this
amplifies, the rate of heat input increases, resulting in fine
paper. The following conclusions can be drawn based on
microstructure, in turn increasing the hardness.
the experiments carried out:
1. The joint fabricated using FSW process parameters
1000 rpm (tool rotational speed), 40 mm/min (weld-
4 Conclusion ing speed), 4 kN (axial load) with the cylindrical tool
profile has the highest yield strength and ultimate
Aluminum alloy AA5083 along with AA6062 can be suc-
tensile strength properties compared to the other
cessfully used for friction stir weld for tool rotational
 Investigation of mechanical behavior of friction stir welded joints of AA6063 | 63

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Aluminum Alloys to Titanium Alloys by Friction Stir Welding”,
2. The flexural strength 227.403 MPa of the weld spec-
Materials Transactions, 52, 948–952, 2011.
imen is lower than the other specimens. Minimum
[4] Da Silva, A. A. M., Arruti, E., Janeiro, G., Aldanondo, E., Alvarez, P.
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